1. Field of the Invention
This invention relates to novel supported catalysts for the polymerization of olefins to polyolefins such as polyethylene, polypropylene and the like, or copolymers such as ethylene copolymers with other alpha-olefins and diolefins. This invention especially relates to the use of halogenated silane compounds, preferably tetra- and trichlorosilanes, in place of chlorine gas and other chlorine-containing compounds as a chlorinating agent for the production of a magnesium-transition metal containing catalyst component of enhanced activity and capable of producing polyolefins in particle form of high bulk density. The use of a chlorinated silane compound as a chlorinating agent during formation of magnesium-titanium catalyst component imparts unusually high activity and improved hydrogen response to a catalyst system and the polymer product obtained has a desirable bulk density compared to a catalyst system using an otherwise similarly prepared catalyst component wherein chlorine gas or other non-silane type of chlorine compounds are used as a chlorinating agent. The improved catalyst components and catalyst systems using such components are especially useful for the production of linear polyethylenes such as high density and linear low density polyethylene. The polymer product produced with such catalyst system has an important balance of polymer properties. For example, the catalyst system produces a polymer with a narrow molecular weight distribution, in particle form of high bulk density, and with a narrow size distribution of spherical particles. In addition, the resins exhibit excellent melt strength during processing resulting in excellent bubble stability during film blowing.
2. Description of the Prior Art
Recently, interest has arisen in the use of magnesium-titanium complex catalyst components for the polymerization of olefins. For example, catalyst components comprising the reaction product of an aluminum alky-magnesium alkyl complex plus titanium halide are disclosed in U.S. Pat. Nos. 4,004,071 and 4,276,191. Each of U.S. Pat. Nos. 4,402,861, 4,378,304, 4,388,220, 4,301,029 and 4,385,161 disclose supported catalyst systems comprising an oxide support; such as silica; an organomagnesium compound, a transition metal compound and one or more catalyst component modifiers. European patent application No. 27733 discloses a catalyst component produced by reducing a transition metal compound with an excess of organomagnesium compound in the presence of a support such as silica and thereafter deactivating the excess organomagnesium compound with certain deactivators including hydrogen chloride.
U.S. Pat. No. 4,136,058 discloses a catalyst component comprising an organomagnesium compound and a transition metal halide compound, which catalyst component is thereafter activated with an activating agent such as hydrogen chloride. This patent does not teach the use of support material such as silica, but otherwise the disclosure is similar to the above-discussed European patent application.
U.S. Pat. No. 4,250,288 discloses a catalyst which is the reaction product of a transition metal compound, an organomagnesium component, and an active non-metallic halide such as HCl and organic halides containing a labile halogen. The catalyst reaction product also contains some aluminum alkyls.
U.S. Pat. Nos. 4,713,547 and 4,263,171, respectively disclose a catalyst component comprising silica, an aluminum-type titanium trichloride and dibutyl magnesium and a catalyst component comprising a magnesium alkyl-aluminum alkyl complex plus titanium halide on a silica support.
The use of chlorine gas in polymerization processes is taught in U.S. Pat. No. 4,267,292 wherein it is disclosed that chlorine gas is to be added to the polymerization reactor after polymerization has been initiated in the presence of a Ziegler catalyst. U.S. Pat. No. 4,248,735 teaches subjecting a silica support to a treatment with bromine or iodine and thereafter incorporating a chromium compound onto the support. U.S. Pat. No. 3,513,150 discloses the treatment of gamma alumina plus titanium tetrachloride with a gaseous chlorinating agent and employing said treated material in combination with a cocatalyst for the polymerization of ethylene.
European patent application No. 32,308 discloses polymerizing ethylene in the presence of a catalyst system comprising an organic metal compound and a titanium-containing material which is obtained by reacting together an inert particulate material, an organic magnesium compound, a titanium compound and a halogen-containing compound such as SiCl.sub.4, PCl.sub.3, BCl.sub.3, Cl.sub.2 and the like.
British No. 2,101,610, discloses the treatment of silica with a magnesium alkyl, an alcohol, benzoyl chloride and TiCl.sub.4. In each of Japanese Kokai Nos. 56-098206 and 57-070107 acyl halides are employed during the preparation of titanium supported catalysts.
The catalyst systems comprising magnesium alkyls and titanium compounds, although generally useful for the polymerization of olefins such as ethylene and other 1-olefins, do not show excellent responsiveness to hydrogen during the polymerization reaction for the control of molecular weight, do not readily incorporate comonomers such as butene-1 for the production of ethylene copolymers, and do not show an extremely high catalytic activity.
In U.S. Pat. No. 4,451,574, a catalyst system obtained by treating an inert particulate support, such as silica, with an organometallic compound, a titanium halide and a halogen gas is disclosed. Although the catalyst obtains very high activities, there is a need for improving the properties of polymer product obtained by polymerizing olefins in the presence of the catalyst and to improve the bulk density of polymer product.
In U.S. Pat. No. 4,564,606 there is disclosed a transition metal supported catalyst component obtained by contacting an inert solid support with (a) the reaction product of a dialkyl magnesium compound and an alcohol, (b) an acyl halide, (c) TiCl.sub.4, and (d) Cl.sub.2. In U.S. Pat. No. 4,565,797 there is disclosed a transition metal supported catalyst component obtained by contacting an inert solid support with (a) the reaction product of a dialkyl magnesium compound and an oxygen-containing compound, (b) a transition metal halide such as TiCl.sub.4, (c) Cl.sub.2 and treating the resulting solid with an organometallic compound of a Group IIa, IIb or IIIa metal. Although these catalysts obtain high activities and improved resin properties, there is a need for improving both activity and response to hydrogen.